) Stress concentrations 



) Size effect and stress distribution 



c ) corros i on fat i gue 



[O) Notch sens i t i v i ty 



|E) Surface conditions and coatings 



F) Stress history 



'Gi Inclusions and directional properties 



H) Residual stresses 



I ) Gra in size 



J) Speed effect 



K) Temperature effect 



L) Cold work 



M) ''Cocoa" or fretting corrosion 



The effects on the fatigue strength of a structural 



MEMBER LISTED UNDER (A) THROUGH (F) AND (M) ARE OF 

 major IMPORTANCE WHEREAS THOSE LISTED UNDER (G) 

 THROUGH (L) are OF MINOR IMPORTANCE. 



The design of the bracing system must take into con- 

 sideration THE possibility OF FAILURE BY BRITTLE 



fracture. a brittle fracture can occur under the 

 influence of a combination of the following factors: 



|A) Low temperature 



B) Hi gh rate of stra i n 



C) Stress concentration 

 ,0} Large values of stress 



Low temperatures and dynamic loading can occur simul- 

 taneously at THE locations OF TEXAS ToWERS. |N ORDER 

 TO AVOID A BRITTLE FRACTURE, SERIOUS STRESS CONCEN- 

 TRATION FACTORS MUST BE MINIMIZED AND PROBABILITY OF 

 FORMATION OF FATIGUE CRACKS OF APPRECIABLE SIZE 

 AVOIDED BY CAREFUL AND CONSERVATIVE DESIGN OF THE 

 BRACING SYSTEM. 



SELF- INDUCED VIBRATIONS 



During a storm the flow of air between the dome struc- 

 tures WILL have an increased VELOCITY DUE TO THE 

 "VENTURI effect" and SELF-INOUCED vibrations DUE TO 



THE "Karman vortex trail" may be set UP, However, it 

 is believed that such self-excited vibrations WILL not 



\k - 



